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Date: Thu, 13 Oct 2016 12:25:30 -0400 (EDT)
From: CAI Qian <caiqian@redhat.com>
To: Dave Chinner <david@fromorbit.com>
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Subject: Re: [bisected] Re: local DoS - systemd hang or timeout (WAS: Re:
 [RFC][CFT] splice_read reworked)
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----- Original Message -----
> From: "Dave Chinner" <david@fromorbit.com>
> Sent: Wednesday, October 12, 2016 4:59:01 PM
> Subject: Re: [bisected] Re: local DoS - systemd hang or timeout (WAS: Re: [RFC][CFT] splice_read reworked)
> 
> On Wed, Oct 12, 2016 at 03:50:36PM -0400, CAI Qian wrote:
> > 
> > 
> > ----- Original Message -----
> > > From: "Dave Chinner" <david@fromorbit.com>
> > > Sent: Monday, October 10, 2016 5:57:14 PM
> > > 
> > > > http://people.redhat.com/qcai/tmp/dmesg
> > > 
> > > It's a page lock order bug in the XFS seek hole/data implementation.
> > So reverted this commit against the latest mainline allows trinity run
> > hours. Otherwise, it always hang at fdatasync() within 30 minutes.
> > 
> > fc0561cefc04e7803c0f6501ca4f310a502f65b8
> > xfs: optimise away log forces on timestamp updates for fdatasync
> 
> Has nothing at all to do with the hang.
> 
> > PS: tested against the vfs tree's #work.splice_read with this commit
> > reverted is now hanging at sync() instead which won't be  reproduced
> > against the mainline so far.
> > http://people.redhat.com/qcai/tmp/dmesg-sync
> 
> It is the same page lock vs seek hole/data issue.
FYI, CVE-2016-8660 was assigned for it.
   CAI Qian